Electrical heating apparatus with a side-positioned in-duct terminal box and a bottom-positioned control box

ABSTRACT

A space heater of the slip-in type adapted for use in a ductwork system has a housing unit including a frame supporting at least one electric-resistance-heating element having a pair of terminals. A bottom-positioned control box containing heating element controls is attached to and positioned at the outside of the housing unit. An enclosed side-positioned, terminal box containing the resistance-heating element terminals and wiring connecting the terminals to the controls in the control box is attached to and positioned within the housing unit substantially at right angles to the control box. The housing unit, the control box and the terminal box are so dimensioned relative to the ductwork system that when the space heater is installed within the ductwork, both the housing unit and the terminal box are recessed within the ductwork while the control box is positioned outside and at the bottom thereof. The terminal box contains thermal cutouts operatively connected to the heating element.

United States Patent [72] Inventor [21] Appl. No. 879,309 [22] Filed Nov. 24, 1969 [45] Patented Nov. 23, 1971 [54] ELECTRICAL HEATING APPARATUS WITH A SIDE-POSITIONED IN-DUCT TERMINAL BOX AND A BO'I'IOM-POSITIONED CONTROL BOX 3,102,185 8/1963 Boyd et a1 2l9/374X 3,176,117 3/1965 Knoll et a1. 219/375 X 3,440,400 4/1969 Cotts 21 /376 X Primary Examiner-A. Bartis AnorneySidney B. Ring ABSTRACT: A space heater of the slip-in type adapted for use in a ductwork system has a housing unit including a frame supporting at least one electric-resistance-heating element having a pair of tenninals. A bottom-positioned control box containing heating element controls is attached to and positioned at the outside of the housing unit, An enclosed sidepositioned, terminal box containing the resistance-heating element terminals and wiring connecting the terminals to the controls in the control box is attached to and positioned within the housing unit substantially at right angles to the control box. The housing unit, the control box and the terminal box are so dimensioned relative to the ductwork system that when the space heater is installed within the ductwork, both the housing unit and the terminal box are recessed within the ductwork while the control box is positioned outside and at the bottom thereof. The terminal box contains thermal cutouts operatively connected to the heating element.

PATENTEDNHV 23 ml 8.622 752 I sum 1 OF 2 FIG .1.

mvewrm JERaME F. BRASCH BY will; 5'

Aflomar ELECTRICAL HEATING APPARATUS WITH A SIDE- POSITIONED IN-DUCT TERMINAL BOX AND A BOTTOM-POSITIONED CONTROL BOX This invention relates to improvements in an electrical heating apparatus and has particular reference to improvements in a resistance-wire'heater which is installed in and forms part of a forced-air heating system.

In recent years forced-air heating has become quite popular. Its use has been accelerated by the fact that an air-conditioning system can also use the same ducts as the forced-air heating system. Furthermore, with the advent of low-cost electricity and better engineering and insulation, the use of forcedair electric heat has become increasingly popular. The simplicity of the design and the use of resistance electric heating units plus the fact that they can be installed economically in a plurality' of places in the duct system with individual unit controls has accelerated the trend. The simplicity of their installation is illustrated by the slip-in" unit of theforced-air ductwork which is inserted into a cutaway duct section.

In the construction of electric resistance wire heaters, the sturdiest design is obtained by installing the resistance wire coils parallel to ceiling or floor. Resistance wire coils are more firmly supported witho'ut sagging in this horizontal position by the proper distribution of bushings in the cross-supports.

Thus, it is customary inthe prior art to design resistance wire heaters with horizontal coils (i.e. parallel to the width of the'duetworks) with control boxes positioned at a side of and outside the duct. A typical design is achieved by having the resistance wire terminals in the control box as well as any other desired auxiliary electrical control and supply feature. By opening the control box, easy access to the terminals and other vital units could be affected. Such features are described in FIG. 1 of Ser. No. 879,412, filed Nov. 24, 1969, which shows the typical construction of the prior art slip-in" type heater.

In addition, Ser. No. 879,412 filed Nov. 24, 1969 in FIG. 4 describes and claims the novel features of a heater containing a recessed-terminal box.Such resistance wire heaters having side-positioned control boxes are generally satisfactory for most installations.

In general, the conventional electric resistance wire heating devices contain the following:

l. A resistance wire housing unit which contains:

1. the frame housing 2. a series of cross-supports attached to the frame housing 3. resistance wire heating elements aligned within the housing frame and supported by the cross-supports.

4. bushings which insulate resistance wires from the cross-supports.

II. The control box which generally contains 1. resistance wire terminals 2. auxiliary electrical control and supply features which may include some, or all, of the following features plus others:

main electrical connections fuses magnetic contactors transformers control terminals automatic reset thermal cutouts (as a primary safety protection when heater'does not have sufficient air flow), etc.

g. manually resettable thermal cutouts or manually replaceable thermalcuto'uts (heat limiters) as secondary safety protection h. pneumatic electric switches i. fused or nonfused disconnects j. pilot lights k. pilot switches l. automatic or nonautomatic circuit breakers m. other features.

Thus, in the'conventional heater there are two general housing units:

l. The resistance wire housing unit when installed fits into the duct.

2. The control box, attached to the resistance wire unit, which is installed outside the air duct.

A typical electric duct heater is illustrated in FIG. 1 of Ser. No. 879,412, filed Nov. 24, 1969, which is called a slip-in" heater; comprising the resistance wire housing unit and the control box. The resistance wire housing unit contains electric resistance coils strung at intervals within the body thereof through insulated holes in the cross-support of resistance wire housing unit. The resistance wire housing unit is installed totally within the duct. The control box, which contains electrical connections and optional auxiliary electrical equipment, is installed outside the duct.

FIG. 3 of Ser. No. 879,412 filed Nov. 24, 1969 illustrates a conventional duct heater and'FlG. 4 of Ser. No. 879,412 filed Nov. 24, 1969 illustrates the recessed terminal box which figures are placed side-by-side to accentuate the differences. In FIG. 4 the resistance coil tenninals and associated features such as heat limiters and automatic reset thermal cutoff, etc. being recessed are subjected to air flow vital to their proper operation.

Note that all of these resistance wire heaters have side-positioned terminals and control boxes, either unitized or separated, for example separated by recessin g as in FIG. 4.

For certain installations, however, such as where two ductworks are side-by-side without adequate space between them and/or where the ceiling or wall prohibits the use of a sidepositioned control box because of lack of space, a side-positioned electric heater cannot be employed.

I have now devised a bottom-positioned heater which has the advantages of the'side-positioned control box type, which is characterizedby a resistance wire housing unit containing a resistance wire terminal box in the normal side position, said resistance wire housing unit and resistance wire terminal box being designed to fit completely within ductworks; and being further characterized by a control box at essentially right angles to the terminal box along the bottom frame of the resistance wire housing unit, said control box being designed to fit outside the ductworks.

By employing this design one achieves all the advantages of the conventional horizontal design while incorporating into the heater the accessibility of a bottom-positioned control box. In addition to inserting all of the heating unit within the confinesof the ductworks without any side projections, the fact that the terminal box is installed totally within the ductwork itself imparts to the resistance wire terminals and associated features, such as heat limiters and the automatic reset thermal cutout, etc. the advantage of being in the air stream of the ductwork which air stream assists in its proper operation.

In a typical commercial installation the in-duct terminal box of the present invention contains resistance wire terminals, automatic reset thermal cutouts and heat limiters all prewired at the factory to the terminal box. The bottom-positioned control box of the present invention has any desired feature normally present in the control box, such as for example contactors, fuses, transformers, etc., examples of which are specified above.

In contrast to theconventional resistance wire heater the present invention in essence contains a true terminal box, (separate and distinct from the control box) containing the resistance wire terminals and related equipment which when installed is side-positioned within the duct. The bottom-posihousing tioned control box (i.e. which is not installed into the ducts) is in essence the true control box (as distinguished from the terminal box) and is installed at the bottom of the outside ducts and at an essentially right angle to the terminal box.

Resistance wire terminals are to be distinguished from field wiring and control terminals usually present in the control box.

The invention will be clearly evident from the present detailed description of the preferred embodiment and the drawing in which:

FIG. 1 is a perspective cutaway view of a heater of this invention having a bottom-positioned control box and a sidepositioned terminal box.

FIG. 2 is a wiring diagram of an illustrative embodiment of this invention.

FIG. 1 illustrates a duct heater of the present invention of the bottom slip-in type wherein l is the resistance wire housing unit frame. The cross-supports 2 are attached at right angles to the sides of the frame. The coiled resistance wires 3 are strung through insulated holes 4 in the cross-supports. It is to be particularly noted that the resistance wire terminals 5, the automatic reset thermal cutout 6 and heat limiters 7 are positioned, when installed, in the terminal box 8 which is within the duct and is thus subjected to the air circulation of the duct. The number and length of coils, cross-supports, insulated holes, etc. will vary with the size and capacity of the par ticular heater.

The bottom-positioned control box 9 is positioned outside the duct and the control box cover 9 can be removed for easy access thereto. The terminals, automatic reset cutout and heat limiters are all wired to terminal blocks in the control box for easy attachment to other features desired in the control box and well as connection to the electrical source.

Because of the variations of features which may be present in the control box, an illustrative wiring diagram is presented in FIG. 2, where 10 is the fused disconnect switch and 11 is the control voltage source entering through the thermostat l2 and line 13. The heater is designated by dotted lines 14 which in turn is divided into those features present in the control box represented by dotted line 15 and those features in the terminal box and in the resistance heating housing unit being represented by dotted line 16. The current passes through the fuses 17 and contactors 18, through the heat limiters l9 and into the resistance heating coils 20. In electrical connection through the contractors is the thermostat l2 and the automatic reset thermal cutout 21.

In essence, the present invention has the following main features:

I. It is bottom positioned in the duct.

2. It has a terminal box positioned in the duct.

3. It has a bottom-positioned control box outside the duct.

Any heater design containing these main features is within the scope of this invention. This invention also includes the presence of auxiliary features such as those illustrated above which may be positioned in the control box.

Although the invention has been described by making detailed reference to a currently preferred embodiment, this detail should be understood solely in an instructive, rather than in a limiting sense, numerous variations being contemplated as within the scope and spirit of this invention.

Having thus described my invention what I claim as'new and desire to obtain by Letters Patent is:

l. A space heater adapted for use in a ductwork system which heater contains a unitary assembly of l. a resistance wire housing unit including a frame housing supporting at least one resistance wire heating element having a pair of terminals;

2. a bottom-positioned control box attached to and positioned at the outside of the resistance wire housing unit, and

3. a side-positioned terminal box which contains the resistance wire tenninals electrically connected to the controls of the control box, said terminal box being enclosed, attached to, and positioned within the resistance wire housing unit substantially at right angles to the bottompositioned control box; said frame housing, said control box and said terminal box being so dimensioned relative to the ductwork system that when the space heater is installed within the ductwork system both the resistance wire housing unit and the terminal box are recessed within the ductwork system while the control box is positioned at the bottom of the ductwork and outside the ductwork system; said terminal box containing thermal cutouts operatively connected to the heatingelement. 2. The space heater of claim 1 which is the slip-1n type. 

1. A space heater adapted for use in a ductwork system which heater contains a unitary assembly of
 1. a resistance wire housing unit including a frame housing supporting at least one resistance wire heating element having a pair of terminals;
 2. a bottom-positioned control box attached to and positioned at the outside of the resistance wire housing unit, and
 3. a side-positioned terminal box which contains the resistance wire terminals electrically connected to the controls of the control box, said terminal box being enclosed, attached to, and positioned within the resistance wire housing unit substantially at right angles to the bottom-positioned control box; said frame housing, said control box and said terminal box being so dimensioned relative to the ductwork system that when the space heater is installed within the ductwork system both the resistance wire housing unit and the terminal box are recessed within the ductwork system while the control box is positioned at the bottom of the ductwork and outside the ductwork system; said terminal box containing thermal cutouts operatively connected to the heating element.
 2. a bottom-positioned control box attached to and positioned at the outside of the resistance wire housing unit, and
 2. The space heater of claim 1 which is the slip-in type.
 3. a side-positioned terminal box which contains the resistance wire terminals electrically connected to the controls of the control box, said terminal box being enclosed, attached to, and positioned within the resistance wire housing unit substantially at right angles to the bottom-positioned control box; said frame housing, said control box and said terminal box being so dimensioned relative to the ductwork system that when the space heater is installed within the ductwork system both the resistance wire housing unit and the terminal box are recessed within the ductwork system while the control box is positioned at the bottom of the ductwork and outside the ductwork system; said terminal box containing thermal cutouts operatively connected to the heating element. 